Efficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy
AffiliationUniv Arizona, Steward Observ
Univ Arizona, Coll Opt Sci
Keywordsinstrumentation: adaptive optics
instrumentation: high angular resolution
MetadataShow full item record
PublisherEDP SCIENCES S A
CitationEfficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy 2017, 604:A122 Astronomy & Astrophysics
JournalAstronomy & Astrophysics
Rights© ESO, 2017
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractPhotonic technologies off er numerous advantages for astronomical instruments such as spectrographs and interferometers owing to their small footprints and diverse range of functionalities. Operating at the diffraction-limit, it is notoriously difficult to efficiently couple such devices directly with large telescopes. We demonstrate that with careful control of both the non-ideal pupil geometry of a telescope and residual wavefront errors, efficient coupling with single-mode devices can indeed be realised. A fibre injection was built within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument. Light was coupled into a single-mode fibre operating in the near-IR (J-H bands) which was downstream of the extreme adaptive optics system and the pupil apodising optics. A coupling efficiency of 86% of the theoretical maximum limit was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and was linearly correlated with Strehl ratio. The coupling efficiency was constant to within <30% in the range 1250-1600 nm. Preliminary on-sky data with a Strehl ratio of 60% in the H-band produced a coupling efficiency into a single-mode fibre of similar to 50%, consistent with expectations. The coupling was >40% for 84% of the time and >50% for 41% of the time. The laboratory results allow us to forecast that extreme adaptive optics levels of correction (Strehl ratio >90% in H-band) would allow coupling of >67% (of the order of coupling to multimode fibres currently) while standard levels of wavefront correction (Strehl ratio >20% in H-band) would allow coupling of >18%. For Strehl ratios <20%, few-port photonic lanterns become a superior choice but the signal-to-noise, and pixel availability must be considered. These results illustrate a clear path to efficient on-sky coupling into a single-mode fibre, which could be used to realise modal-noise-free radial velocity machines, very-long-baseline optical/near-IR interferometers and/or simply exploit photonic technologies in future instrument design.
NoteOpen access journal.
VersionFinal published version
SponsorsJSPS [23340051, 26220704, 23103002]; Astrobiology Center (ABC) of the National Institutes of Natural Sciences, Japan; Subaru Telescope; Australian Research Council Centre of Excellence for Ultrahigh bandwidth Devices for Optical Systems [CE110001018]